Two-zone pump



TEMPLE R HOFFER INVENTOR.

ATTORNEYS 3 Sheets-Sheet 1 T P HOFFER TWO-ZONE PUIP FIG.2

FIG.E

Sept. 19, 1950 Filed Nov 4, 1946 R m. 5 2 \\H@ E i4 MR m a t 2 9w 8 5WNGM m u a wjmw v CM em 4m MM w x V 9 v A 9m t a B 3 W 3% T h S 3 II IFIG. 5 My T. P. HOFFER TWO ZONE PUIP Sept. 19, 1950 Filed Nov. 4, 1946Sept. 19, 1950 Filed Nov. 4, 1946 T. P. HOFFER TIC-ZONE PUMP 3Sheets-Sheet 3 Temp/e Hoffer INVENTOR.

Patented Sept. 19, 1950 TWO-ZONE PUMP Temple 1'. Hoi'fer, Dallas, Tex.,assignor to Otis Pressure Control, Inc., Dallas, Tex., a corporation ofDelaware Application November 4, 1946, Serial No. 707,653

14 Claims.

1 This invention relates to improvements in well production apparatusand refers more particularly to apparatus or equipment for separatelyproducing fluid from two producing formations through a single wellbore.

In wells having multiple producing formations it is usually desirable toproduce from the formations separately without commingling the fluidfrom the formations. Obviously this should be accomplished by usingconventional equipment as far as possible.

It is further desirable that the apparatus permit flow from either ofthe formations while flow is induced from the other formation by meansof pumps, gas lift or the like. To accomplish these ends two flowpassages must be provided within a well bore, each of the passagescommunicating with one of the producing formations with means forinducing flow of fluid separately in each of the passages.

An object of this invention is to provide for a well bore having twoproducing formations apparatus for conducting fluid to the surfacewherein the casing tubing annulus is utilized as a conduit for fluidfrom one formation and the tubing for fluid from the other formation,

Another object of this invention is to provide apparatus for a well borehaving two producing formations apparatus for conducting fluid to thesurface wherein the casing tubing annulus is utilized as a passage forfluid from one formation and the tubing sucker rod annulus for fluidfrom the other formation, wherein means may be provided for inducingflow of fluid through each annulus.

A further object is to provide pumping apparaproducing formation tus forwells having multiple producing formations wherein a single sucker rodstring may be utilized to induce flow from the formations.

Yet another object is to provide pumping apparatus for wells havingmultiple producing formations wherein a single sucker rod string may beutilized to produce from the formations and the sucker rod string may beof conventional type substantially throughout its length.

Yet a further object is to provide apparatus of the type described inwhich the tendency of the pump to gas lock is eliminated.

Other and further objects of this invention will appear from thefollowing description:

In the accompanying drawings which constitute a part of the instantspecification and are to be read in conjunction therewith and whereinlike reference numerals are used to indicate like parts in the variousviews;

Figs. 1, 2 and 3 are complementary sectional views of the lower portionof a well bore communicating with two producing formations which isequipped with apparatus embodying this in-, vention;

Fig. 4 is an enlarged detail of the annular traveling valve and aportion of the hollow plunger of the apparatus shown in Fig. 2;

Fig. 5 is an enlarged detail of the packer and standing valve in thetubing-hollow rod annulus illustrated in Fig. 2; and

Fig. 6 is a vertical sectional view of the complete apparatus installedin a well bore.

Referring to the drawings, numeral Hi designates a well bore extendingdownwardly through the upper producing formation II and the lower II.The well bore is equipped with an oil string of casing It and a stringof flow tubing it. The oil string of casing and the flow tubing areperforated or may have other suitable means of communication with theproducing formations II and 12.. A rod string is mounted forreciprocation within the tubing and is made up principally of twosections. The usual solid sucker rod string [5 extends downwardly fromthe ground surface to a level somewhat above the upper producingformation. At its lower end the solid sucker rod string l5 carries ahollow polished rod section IS. The hollow section l6 communicates atits lower end with the lower producing formation through the lower endof the flow tubing. This hollow rod section also communicates at itsupper end with the interior of the flow tubing and suitable means foraccomplishing this is shown in Fig. 1 wherein a perforated collar orcross-over connection I1 is illustrated as a coupling member between thesolid rod string and the hollow rod section.

It will be understood that with the apparatus thus far describedboth theproducing formations are in communication with the interior of thecasing, tubing and hollow rod section. Thus, it is necessary to dividethe annular spaces between the casing and tubing and tubing and rodstring into separate chambers in order to provide separate flow passagesfor fluid from the two producing formations. Preferably each of theannular spacesare divided into upper, lower and intermediate chambers.Conventional packers it are provided for the casing tubing annulusatlevels above and below the upper producing formation. Thev tubing I4is perforated at Ma above the upper packer l8.

Due to the arrangement thus far described fluid from formation llcommunicates with the interior of the casing intermediate packers l8 andmay pass through the tubing perforation 4| into the interior of thetubing and through ports a into the interior of the casing above theupper packer. In order to separate this flow passage from fluid from thelower producing formation packers l9 and 20 are placed in the annulusbetween the tubing and hollow rod section. Packer I9 is located adjacentand above perforations I la while packer 20 is positioned adjacent andbelow tubing perforations 4| communicating with the interior of thecasing intermediate packers l8. Thus a sealed flow passage is providedfrom the upper producing formation to the upper chamber of the casingtubing annulus and the fluid may then flow to the ground surface throughthis annulus.

By reference to Figs. 1, 2 and 3 it will be seen that there has alsobeen provided a separate flow passage for fluid from the lower formation[2 to the ground surface. This passage includes the lower end of tubingI4 the interior of the hollow polished rod section I 6 and the interiorof tubing l4 above the upper packer I 9. The fluid may then flow to theground surface through the tubing sucker rod annulus.

If both the producing formations H and I2 are capable of natural flowfurther apparatus is not required in the well bore. However, after thewells are produced for a prolonged period it usually becomes necessaryto employ means for inducing flow from either or both of the formations.According to this invention this may be readily accomplished byutilizing the sucker rod string and polished rod section as an actuatingrod for a plunger or other type pump or pumps operable to force fluidthrough both of the fluid passages heretofore described.

To induce flow from the lower formation the lower end of the hollowpolished rod section it carries a part with an enlarged diameter asshown at 2i. This part has a close fit with the inner surface of asection of tubing Md which is finished inside to provide a pumpingcylinder and upon reciprocation of the sucker rod string part 2! servesas a plunger. This plunger is equipped with a traveling valve which maycomprise a ball 22 operable with seat 23. The usual standing valve 24 islocated in the interior of tubing I, at a point intermediate the lowertubing perforations and the lower end of the pumping cylinder d. Thusupward movement of plunger 2! draws fluid past the standing valve 25.The standing valve is then seated on the downward movement of plunger 2|and fluid above the standing valve is permitted to flow through thetraveling valve 22. On the next upward stroke of plunger 2| the fluidabove the traveling valve is raised and thus continued reciprocationinduces flow of fluid from the lower formation through the hollow rodsection It and into the interior of tubing l4 above packer i9 and thenceto the ground surface.

The same rod string is preferably utilized to actuate a plunger andtraveling valve assembly operable in the annular chamber within thetubing intermediate packers i9 and 20 and above the tubing perforationscommunicating with formation II, in a section of tubing Me which isfinished inside to provide a second pumping cylinder. An annularstanding valve is also provided to cooperate in the usual fashion withthe plunger and traveling valve. This mechanism is detailed in Figs. 4and 5.

Referring now to the annular traveling valve shown in Fig. 4, it will beseen that the hollow rod section l6 has a tapered portion |6a which hasa press fit with an annular ring 25 which constitutes the travelingvalve seat. This ring may be connected to the rod section I6 in anysuitable manner. The ring 25 has vertical ports 25a to establishcommunication past this member. Ring valve 26 fits loosely over" thehollow section I6 and has a tapered seating surface corresponding to theseating surface of ring 25. Thus, with the pressure differential acrossring 25 tending to produce flow upwardly through the tubing, ring 28 isunseated. However, when the pressure differential tends to causedownward flow through the tubing, ring valve 26 is seated to close thevalve.

The plunger includes a hollow member 21 which is carried by ring 25.Member 21 has a close fit with the interior of the tubing as will beunderstood by those skilled in the art.

With regard to the standing valve detailed in Fig. 5 it comprises anannular seat member 28. The seat member has a sliding fit on rod mm Ption l6 and is anchored to the tubing in a manner to be hereinafterdescribed. The seat member has ports communicating with perforations intubing l4 and with the annular space within tubing I4 and above member28. Flow through the ports is controlled by an annular valve member 33loosely carried by rod section I6. Valve member 33 has a seating surfacecooperable with that of seating member 28. A seal is provided betweenthe member 28 and tubing I 4. This may be suitably accomplished by useof chevron type packing rings 29, spacer rings 30 and 3! and gland nut32.

The standing valve assembly just described is preferably connected topacker unit 20 and with the packer is adapted to be anchored in properposition within tubing M. This packer unit includes a carrier sleeve 34having a portion of reduced diameter threaded into the lower end or thebore through member 28. Suitable seal rings such as chevron type packingmaterial 35 is secured about the portion of reduced diameter of member34 and is held in place between shoulders 33a of the packer carrier andthe lower end of seat member 28. Spacer rings may be employed in thispacker assembly as shown. It is to be understood that any suitablepacking material or assembly may be used in this connection. Can'ier 34also is provided with packing material 36 carried by a portion of itsbore of enlarged diameter to provide a sliding seal about hollow rodsection IS. The packing and suitable spacer rings are held in place inthe bore by means of gland nut 31. Thus it will be seen that the annularspace between tubing [4 and rod section l8 has been effectively sealedoff.

In order to anchor the packer 20 and its associated standing valvewithin tubing 14 an annular groove Mb is provided within the tubingspaced at a predetermined position below the tubing perforations whichcommunicate with the upper producing formation. Anchor rods 38 arecarried by nut 31. These rods have lugs 38a adapted to engage groove bas shown in Fig. 5. Grooves Mb have a greater width than the spacebetween the joints of tubing l4. Lugs 38a are longer than the spacebetween adjacent joint ends of tubing I 4 whereby in passing the suckerrod downwardly through the tubing the lugs 38a will not engage thegrooves between the tubing ends of adjacent joints but will engage thegroove Mb. The hollow rod section It has secured thereto an annularelement 38 having a tapered surface 39a which is adapted to engage thelower inturned downwardly extending portion of anchor rods 38. If it isdesired to release the anchoring means for racking 20, the rod string islifted until element 39 engages the lower ends of rods 38. Thiscollapses rods 38 to disengage lugs 38a from groove 1422. Continuedupward movement of the rod string then serves to withdraw the rod stringand packing unit from the tubing. When the rod string is lowered intothe tubing, axial movement of packer 20 and the associated standingvalve is limited by engagement with the coupling member between adjacentjoints of the hollow rod section It.

Packing i9 may be made up the same as packing 20 except that a suitablegland nut is used in conjunction with the upper end of the packingcarrier to collapse packing 35 instead of the seat ring member 28. Thispacker carries anchoring rods 40 with lugs 40a adapted to engage agroove l4c in the tubing just above the perforations l4a of the tubing.The width of groove I40 and the length of lugs 40a are greater than thewidth of the space between adjacent tube joint ends so that the lugs 40ado not engage the tubing joint ends in lowering or withdrawing the rodstring intoor from tubing 14.

However, groove Me is somewhat narrower than the length of lugs 38a.associatedwith the anchor for packer 20, whereby lugs 38a. willpassgroove I40 as the'rod string is. moved" axially within tubing l4. Asecond element 39 1con nected to the rod string, serves'to*release .the

anchor rods 40.

It is believed that the assembly .andyopera-j tion of the device isobvious from the;foregoing description. Conventional solid sucker rodsare utilized except for the hollow rod section i6,

the well bore, reciprocation of the rod string actuates the hollowplunger 2| and its associated traveling valve to cause upward flow offluid from the lower formation through the hollow rod section and intothe tubing sucker rod annulus above the upper packer [9. This flow thencontinues to the ground surface through the: tubing and is separate fromthe flow through the upper producing formation H. Fluid from the upperformation is simultaneously pumped through the annular chambers betweenthe casing and tubin; and the tubing andhollow rod and back into thecasing tubing annulus above the uppermost packer i8. Reciprocation ofthe rod string actuates the plunger and traveling valve assemblyincluding sleeve 21, seat ring 25 and valve 28. The fluid is drawn pastthe standing valve including seat 28 and ring valve 33 when the rodstring moves upwardly. On downward movement of the rod string thestanding valve is closed and fluid passes through ports 25a and pastring valve 26 of the traveling valve.

It is contemplated that this arrangement of pumping apparatus may beused in wells wherein fluid from either or both the producing formationsflows partially under pressure within the particular formation. Thetraveling and standing valves in each of the passages leading from theproducing formations will in no way interfere with upward fluid flowfrom any connection. It is further contemplated that a different type ofplunger or non-plunger pump may be employed with the flow arrangementdescribed;

which extends from a, point above packer IE to the plunger 2| just abovethe lower formation l2 of the well bore. The tubing and easing are ofthe conventional type with the exception of the grooves Nb and Me inappropriate tubing joints and the sections finished to provide pumpingcylinders. The perforations of the tubing, such as at Ma, may be made inany manner customary to the well producing art. The hollow rod sectionI6 is assembled with the plunger 2| connected to its lower end. Thisplunger carries the traveling valve associated therewith and thestanding valve 24 is secured within the well tubing before it is loweredinto the casing. The packer 20, ring seat 28 and ring 33 are assembledon the hollow rod section as is the plunger, traveling valve assembly,including sleeve 21, seat 25 and ring valve 26. The rod string may thenbe lowered into position within tubing 14 and when anchor rods 38 and 40reach the grooves 14b and He, respectively, in the tubing, the lugsengage the grooves to secure the packing assembly within the tubing.These anchor rods may be released. to permit withdrawal of the rodstring, by lifting up on the rod strin'n This raises elements intoengagement with the lower ends of anchor rods 38 and 40 to release lugs38a and 40a from engagement with grooves Nb and I40, respectively.

The packers I! which separate the casing tubing annulus into separatechambers may be of any conventional type now employed in-the industry.

In operation, with the apparatus assembled in not in a limiting sense.

in will'be seen that the objects of the invention'whave beenaccomplished. There has been .providedjseparate-flow passagescommunicating between the two producing formations and the groundsurface whereby there is no commingling .of the fluids from theformations.

The fluid may flow naturally from either formation, where this ispossible, and the construction is such that separate flow inducing meansmay be utilized in one or both of the passages. The arrangement is suchthat reciprocation of a single rod string, which is conventionalthroughout most of. its length, may be utilized to simultaneouslyactuate pumps in each of the flow passages.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forthtogather with other advantages which are obvious and which are inherentto the structure.

It will be understood that certain features and subcombinations are ofutility and may be emplayed without reference to other features andsubcombinations. This is contemplated. by and is within the sco e of theclaims.

As many ossible embodiments may be made of t e invention withoutdeparting from the scop thereof it is to be understood that all matterherein set forth or shown in the accompanying drawings is to ,beinterpreted as illustrative and Having described my invention, Iclaim: 1. In a well bore communicating with two producing format ons, anoil string of easing, a flow tubing withinthecasing. a solid sucker rodstring mounted for reciprocation withinthe tubing. a hollow rod sectionon the solid sucker rod stri g. means dividing the annular spacesbetween the rasing and tubing and the tubing and hollow rod section intoseparate-chambers means establishing communication between certain ofthe chambers and between the hollow-rod section trol flow through saidseparate passages upon reciprocation of the hollow rod.

2. In a well bore communicating with two producing formations, an oilstring of casing, a flow tubing within the casing, a solid sucker rodstring mounted for reciprocation within the tubing and means associatedwith the casing, tubing and sucker rod dividing the annularspacestherebetween into separate flow passages from the producing formationswhereby fiuid from one formation flows through the upper portion of thecasing to the ground surface and fluid from the other formation flowsthrough the upper portion of the tubing to the ground surface, saidmeans including a rollow rod section connected in the sucker rod stringand forming a part of the passage which includes the upper portion ofthe tubing, and means carried by the hollow rod section forsimultaneously inducing flow through said passages.

3. In a well bore communicating with two producing formations andequipped with an oil string of easing, a flow tubing within the casingand a solid sucker rod string reciprocally mounted within the tubing,said sucker rod string carrying a hollowrod section; packer meansdividing the spaces between the casing and tubing and the tubing andhollow rod section into upper, lower and intermediate chambers; ports inthe tubing and casing placing said intermediate chambers and the uppercasing chamber in communication with each other and one of the producingformations, providing a flow passage for fluid from this formation tothe ground surface; said hollow rod section communicating with the otherformation and upper tubing chamber and providing a flow passage forfluid from this formation; and means having an actuating connection withthe hollow rod section for controlling and inducing flow separately fromsaid formations.

4. In a well here communicating with two producing formations andequipped with an oil string of easing, a fiow tubing within the casingand a solid sucker rod string reciprocally mounted within the tubing,said sucker rod string carrying a hollow rod section; packer meansdividing the spaces between the casing and tubing and the tubing andhollow rod section into upper, lower and intermediate chambers; portmeans in the tubing and casing placing said intermediate chambers andthe upper casing chamber in communication with each other and with theupper producing formation and thus providing a flow passage for fluidfrom this formation to the ground surface; said hollow rod sectioncommunicating with the lower formation and upper tubing chamber and thusproviding a part of a flow passage for fluid from this formation; andmeans having an actuating connection with the hollow rod section forcontrolling and inducing flow separately from said formations.

5. In a well bore communicating with two producing formations andequipped with an oil string of casing, a flow tubing within the casing,and a solid sucker rod string reciprocally mounted within the tubing,said sucker rod string carrying a hollow rod section; packer meansdividing the spaces between the casing and tubing and the tubing andsucker rod string into upper, lower and intermediate chambers; ports inthe tubing and casing placing said intermediate chambers and the uppercasing chamber in communication with each other and the upper producingformation, and thus providing a flow passage for fluid from thisformation to the ground surface; said hollow rod section communicatingwith the lower formation and upper tubing chamber and thus providing aflow passage for fluid from this formation; and two pumping assembliesoperably associated with the sucker rod string and hollow rod sectionfor controlling and inducing flow separately from said formations, saidassemblies each including a plunger, traveling valve and standing valve.

6. In a well bore communicating with two producing formations andequipped with an oil string of casing, a flow tubing and a solid suckerrod string mounted for reciprocation within the tubing, a hollow rodsection carried by the sucker rod string, perforations in the casing andtubing placing the upper producing formation in communication with theinterior of the tubing, casing packers between the casing and tubing onboth sides of the perforations and upper formation, two tubing packersbetween the tubing and hollow rod section, one of these packers at alevel above the upper casing packer and the other at a level below saidtubing perforations, ports in the tubing communicating with the casingabove the upper casing packer and below the upper tubing packer,standing and traveling valves controlling flow through the tubingbetween the ports, said traveling valve operably mounted on the hollowrod section, said hollow rod section slidably extending through thetubing packers, the interior of said hollow section communicating at oneend with the interior of the tubing above said tubing packers and at theother end with the lower producing formation, and standing and travelingvalves controlling flow through said hollow rod section.

7. As a subcombination an elongated tubular member, a hollow rod sectionmounted for reciprocation within the tubular member, two packersremovably anchored between the member and hollow rod section, one of thepackers located adjacent but below the upper end of the hollow sectionand the other located intermediate the ends of the hollow section, portsin the tubular mem ber adjacent and intermediate the packers, a plunger,traveling valve and standing valve associated with the hollow sectionand adapted to induce flow upwardly therethrough, a second plunger,traveling valve and standing valve associated with the hollow sectionexterior thereof, within the tubular member and between the packers, thelatter plunger traveling valve and standing valve adapted to induce andcontrol flow upwardly through the tubular member intermediate the ports.

8. As a subcombination a unit adaptable for use in a well bore equippedwith a well tubing and casing, said unit comprising a hollow rod sectionhaving openings at both ends and adapted to be connected to a solidsucker rod string, a plunger at the lower end of said hollow section, atraveling valve associated with the plunger and adapted to control flowthrough the plunger and section, two spaced apart packers mounted onsaid section an annular plunger secured to the hollow section exteriorthereof and a traveling valve associated therewith adapted oninstallation of the hollow rod section within the well tubing to controlflow through that portion of the tubing and past said valves, saidannular plunger and traveling valve located intermediate the packers.

9. As a subcombination a unit adaptable for use in a well bore equippedwith a well tubin and casing, said unit comprising a hollow rod sectionhaving openings at both ends and adapted to be connected to a solidsucker rod string, a plunger at the lower end of said hollow section, atraveling valve associated with the plunger and adapted to control flowthrough the plunger and section, two spaced apart packers mounted onsaid hollow section, an annular plunger secured to the hollow sectionexterior thereof and intermediate the packers, a traveling valveassociated with the plunger, a standing valve slidable on the hollowsection intermediate the packers, said plunger and valves adapted oninstallation of the unit within the well tubing to control flow throughthat portion of the tubing between the packers and p 1 the valves.

10. In a well bore communicating with two producing formations, a stringof casing, a string of tubing within the casing, a string of solidsucker rod mounted for reciprocation within the tubing, a hollow-rodsection secured to the lower end of the sucker rod, and means includingpackers and ports dividing the interiors of the casing, tubing andhollow-rod section into two separate passages for producing well fluidsfrom the formations without commingling the fluids, one part of one ofthe passages including the interior of the hollow-rod section and onepart of the other passage including at least a part of the space betweenthe tubing and hollow-rod section.

11. In a well bore communicating with two producing formations, a stringof easing, a string of tubing within the casing, a string of solidsucker rod mounted for reciprocation within the tubing, a hollow-rodsection secured to the lower end of the sucker rod, means includingpackers and ports dividing the interiors of the casing, tubing andhollow-rod section into two separate passages for producing well fluidsfrom the formations without commingling the fluids, one part of one ofthe passages including the interior of the hollow-rod section and onepart of the other passage including at least a portion of the spacebetween the tubing and hollow-rod section, and two means carried by thehollowrod section and residing respectively within the latter parts ofthe two passages for inducing and controlling the flow therethrough uponreciprocation of the hollow-rod section.

12. In a well bore communicating with two producing formations, a stringof casing, a string of tubing within the casing, a solid sucker rodstring mounted iorreciprocation within the tubing, a hollow-rod sectionsecured to the lower end of the sucker rod, means including packers andports dividing the interiors of the casing, tubing and hollow-rodsection into two separate passages for producing well fluids from theformation without commingling the fluids, one part of one of thepassages including the interior of the hollow-rod section and one partof the other passage including at least a part of the space between thetubing and hollow-rod section, and two travelingand standing-valveassemblies associated with the hollow-rod section for con- 10 trollingfluid flow from the two formations, one traveling valve residing withinthe hollow-rod section and the other traveling valve surrounding thehollow-rod section.

13. In a well bore, communicating with two producing formations, astring of easing, a string of tubing within the casing, said stringsextending substantially to the lower formation, two packers between thecasing and tubing, one of the packers above the upper producingformation and the other located intermediate the formations, a solidsucker rod mounted for reciprocation within the tubing, a hollow-rodsection carried at the lower end of the sucker rod, packer means carriedby the hollow-rod section adapted to be releasably anchored within thetubing to provide seals between the tubing and hollow section, saidpacker means mounted upon the hollow section in such manner that thepacker means may be lowered into and withdrawn from anchored positionwithin the tubing by axial movement of the hollow-rod section, portmeans in the casing, tubing and hollow-rod section providing, togetherwith the casing tubing annulus, the tubing hollow-rod annulus, tubingsuctionrod annulus and the interior of the hollow-rod section, separateflow passages for separately conducting well fluids from both producingformations.

14. In a well bore, communicating with two producing formations, astring of casing, a string of tubing within the casing, said stringsextending substantially to the lower formation, two packers between thecasing and tubing, one of the packers above the upper producingformation and the other located intermediate the formations, a solidsucker rod mounted for reciprocation within the tubing, a hollow-rodsection carried at the lower end of the sucker rod, packer means carriedby the hollow-rod section adapted to be releasably anchored within thetubing to provide seals between the tubing and hollow section, saidpacker means mounted upon the hollow section in such manner that thepacker means may be lowered into and withdrawn from anchored positionwithin the tubing by-axial movement of the hollow-rod section, portmeans in the casing, tubing and hollow-rod section providing, togetherwith the casing tubing annulus, the tubing hollow-rod annulus, tubingsuctionrod annulus and the interior of the hollow-rod section, separateflow passages for separately conducting well fluids from both producingformations, and two traveling valve means carried by the hollow section,residing in the separate flow passages respectively, and removable withthe hollow-rod section for inducing flow of fluids from both formationsupon reciprocation of the hollow-rod section.

TEMPLE P. HOFFER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 967,498 Clark Aug. 16, 19101,870,137 Parker Aug. 2, 1932 2,281,899 White May 5, 1942 Disclaimer2,522,825.-Temple P. H offer, Dallas, Tex. Patent dated Sept. 19, 1950.Two- ZONE PUMP. Disclaimer filed J an. 21, 1952, by the inventor and theassignee, Otis Pressure Gantrol, I no.

Hereby enter this disclaimer to claim 1 of said patent.

[Ofiicial Gazette Febmm'y 19, 1.952.]

